1. Field of the Invention
The present invention relates to a burst scheduling method in an Optical Burst Switching (OBS) system, and more specifically, to a burst scheduling method in an OBS system which grants a high priority to a burst which has used many network resources, such that fairness between bursts can be guaranteed in an OBS system having a mesh-type network. Therefore, it is possible to minimize a burst loss in a network node, thereby enhancing the overall system performance.
2. Description of Related Art
In general, when a burst is generated in Optical Burst Switching (OBS) networks, a Burst Control Packet (BCP) is transmitted first. Then, a Data Burst (DB) for transmitting data is transmitted after a predetermined time. Such a time difference is referred to as an offset time.
A conventional burst scheduling method in the OBS is designed in such a manner that a burst transmitted to the next node via a current node, that is, a Transit Data Burst (TDB) and a burst leaving at the current node attempt to occupy an output channel at the same time such that a burst having a larger offset time can occupy the output channel.
In a mesh-type network, however, various offset times are provided depending on the number of nodes through which a burst should pass so as to arrive at its destination node. Therefore, even bursts having the same priority have a different offset time, which is a cause of obstructing fairness between bursts. Thus, an improvement therefor is needed.
To solve such a problem, a method is proposed in which bursts arriving at a destination node via a plurality of nodes, that is, Several Hop Going (SHG) bursts, are transmitted to the next node using a dedicated wavelength, and bursts in which the destination node is the next node, that is, One Hop Going (OHG) bursts, are inserted between bursts which are transmitted from the previous node and are survived in competition, that is, Transit Data Bursts (TDBs), and are then transmitted.
Such a conventional method can enhance the performance of the OHG burst, but does not present a process of enhancing the performance of the SHG burst, which is transmitted from the previous node and is then transmitted to the next node. Thus, an improvement therefore is needed.
Meanwhile, a ratio of OHG traffic in the overall traffic of the OBS is about 1/N. In order to enhance system performance, a loss of TDB or SHG burst should be reduced.